Optimization and sensitivity analysis of magneto-hydrodynamic natural convection nanofluid flow inside a square enclosure using response surface methodology

This article studies buoyancy-driven natural convection of a nanofluid affected by a magnetic field within a square enclosure with an individual conductive pin fin. The effects of electromagnetic forces, thermal conductivity, and inclination angle of pin fin were investigated using non-dimensional parameters. An extensive sensitivity analysis was conducted seeking an optimal heat transfer setting. The novelty of this work lies in including different contributing factors in heat transfer analysis, rigorous analysis of design parameters, and comprehensive mathematical analysis of solution domain for optimization. Results showed that magnetic strength diminished the heat transfer efficacy, while higher relative thermal conductivity of pin fin improved it. Based on the problem settings, we also obtained the relative conductivity value in which the heat transfer is optimal. Higher sensitivity of heat transfer was, though, noticed for both magnetic strength and fin thermal conductivity in comparison to fin inclination angle. Further studies, specifically with realistic geometrical configurations and heat transfer settings, are urged to translate current findings to industrial applications.

     

Di- and Tetracyano-Substituted Pyrene-Fused Pyrazaacenes: Aggregation in the Solid State

Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown and the crystal packing studied by DFT calculations (transfer integrals and reorganization energies) to get insight into possible use for semiconducting charge transport.     

Nonlinear vibration of the spiral bevel gear with a novel tooth surface modification method

Meccanica - The issue of gear noise is fairly common in power transmission systems. This noise largely stems from the gear pairs vibration triggered by transmission error excitation. This is mainly...     

Graphene oxide‐induced polymerization and crystallization to produce highly conductive polyaniline/graphene oxide composite

Graphene oxide (GO)–polyaniline (PANI) composite is synthesized by in situ polymerization of aniline in the presence of GO as oxidant, resulting in highly crystalline and conductive composite. Fourier transform infrared spectrum confirms aniline polymerization in the presence of GO without using conventional oxidants. Scanning electron microscopic images show the formation of PANI nanofibers attached to GO sheets. X‐ray diffraction (XRD) patterns indicate the presence of highly crystalline PANI. The sharp peaks in XRD pattern suggest GO sheets not only play an important role in the polymerization of aniline but also in inducing highly crystalline phase of PANI in the final composite. Electrical conductivity of doped GO–PANI composite is 582.73 S m^?1, compared with 20.3 S m^?1 for GO–PANI obtained by ammonium persulfate assisted polymerization. The higher conductivity appears to be the result of higher crystallinity and/or chemical grafting of PANI to GO, which creates common conjugated paths between GO and PANI. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1545–1554     

Multivariate optimization of the hollow fiber-based liquid phase microextraction of lead in human blood and urine samples using graphite furnace atomic absorption spectrometry

The present study developed a liquid-phase microextraction based on hollow fiber coupled with graphite furnace atomic absorption spectrometry for the effective extraction and quantitation of lead from urine and blood samples. A multivariate design was used for the optimization of the experimental conditions to ensure high extraction efficiency. Six factors (solvent type, chelating agent, time extraction, temperature, donor phase pH, and acceptor phase pH) were obtained by screening eleven factors of the Plackett–Burman design; these were optimized using the central composite design of response surface methodology. The optimum conditions of donor phase pH, acceptor phase pH, temperature, and extraction time were 5, 9.5, 40 °C, and 120 min, respectively. In addition, oleic acid containing dicyclohexyl-18-krone-6 was used for the membrane phase. Under optimal conditions, the enrichment factor, limit of detection, and limit of quantification were obtained in the ranges of 21.3–18.7, 0.001–0.002 ng mL^?1, and 0.008–0.01 ng mL^?1, respectively, in urine and blood samples. The linearity of the calibration curve was established for the concentration of Pb in the range of 1–50 ng mL^?1 (r²?=?0.9983). Finally, the performance of the developed method was evaluated for the determination of lead in urine and blood samples, and satisfactory results were obtained (RSDs <?10% with recovery >?95).     

Spectrophotometric and conductometric study of complexation of salophen and some transition metal ions in nonaqueous polar solvents

The complexation reaction between Cu(2+), Co(2+) and Ni(2+) metal cations with N,N'-bis(salicylidene)-1,2-phenylenediamine (salophen), in three nonaqueous polar solvents such as: acetonitrile (AN), dimethyl sulfoxide (DMSO), methanol (MeOH) and two binary mixtures of AN:DMSO and AN:MeOH at 25 degrees C were studied by spectrophotometric and conductometric methods. All investigated metal ions form 1:1 ML complex which their stability constants were determined and increase as Irving-Williams stability order of Co(2+)相似文献   

Fabrication of bulk-modified carbon paste electrode containing alpha-PW12O40(3-) polyanion supported on modified silica gel: Preparation, electrochemistry and electrocatalysis

Alpha-PW(12)O(40)(3-) (PW(12)) supported on the surface of silica gel derivatized by 3-aminopropyl(triethoxy)silane (devoted briefly as SiNH(3)PW(12)) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry. There is an ionic bonding character between PW(12) and the surface amino groups of modified silica, which greatly improves the stability of SiNH(3)PW(12)-modified carbon paste electrode due to insolubility of silica gel in water. The SiNH(3)PW(12) bulk-modified carbon paste electrode not only maintains the electrochemical activity of PW(12), but also exhibits remarkable advantages of renewability, as well as simple preparation and inexpensive material. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of IO(3)(-) and hydrogen peroxide. The SiNH(3)PW(12)-CPE is successfully applied as an electrochemical detector to monitor IO(3)(-) in flow injection analysis (FIA). The catalytic peak current was found to be linear with the IO(3)(-) concentration in the range 5x10(-6) to 1x10(-3)molL(-1). The detection limit of the proposed method was found to be 3.1x10(-6)molL(-1) for IO(3)(-) determination.     

Stereoselective synthesis of helical dihydrodipyrrolophenanthroline and hindrance hexa tert‐butyl carboxylatodipyrrolophenanthroline from reaction between 1,10‐phenanthroline and dialkyl acetylenedicarboxylates

High hindrance Hexa tert‐butoxy carbonyl dipyrrolophenanthroline and helical dihydropyrrolophen‐anthroline compounds were prepared from reactions between di tert‐butyl acetylenedicarboxylate and 1,10‐phenanthroline in polar solvents media.     

Succinimidinium N-sulfonic acid hydrogen sulfate as an efficient ionic liquid catalyst for the synthesis of 5-arylmethylene-pyrimidine-2,4,6-trione and pyrano[2,3-d]pyrimidinone derivatives

Research on Chemical Intermediates - Succinimidinium N-sulfonic acid hydrogen sulfate ([SuSA-H]HSO4) as a new ionic liquid is prepared and characterized using a variety of techniques, including...     

An improved second moment method for solution of pure advection problems

The second moment numerical method (SMM) of Egan and Mahoney [Numerical modeling of advection and diffusion of urban area source pollutant. Journal of Applied Meteorology 1972; 11 : 312–322] is adapted to solve for the pure advection transport equation in a variety of flow fields. SMM eliminates numerical diffusion by employing a procedure that takes into account the first and second moments of mass distribution in each grid element. For pure translational flow fields, the method is conservative, positive definite and shape‐preserving. In rotational and/or shear flows, the accuracy of SMM is significantly reduced. Two improvements are presented to make the SMM applicable to a wider range of flow problems. It is shown that the improved SMM (ISMM) is less diffusive and more shape‐preserving than the SMM in rotational and/or deformational flows. The ISMM can also be used to solve for a color function in compressible flow fields. The computational efficiency of this method is compared with that of other methods and, for a given accuracy, it is shown that ISMM is a cost‐effective, non‐diffusive and shape‐preserving method. Copyright © 2000 John Wiley & Sons, Ltd.